Renix slow crank issue

So I know Renix engines typically crank a little slow, but this is something else.

Every morning for the last two weeks my Jeep has had a really really slow crank. Almost as if the battery is weak. But the battery (optima blue top) shows over 12v. I let the Jeep sit for two days, and without starting it I tested the battery. Still showed 12v.

The starter is about 2 years old, I don't really think that's the issue.

After starting and driving, the slow crank issue goes away. But if it sits over night, it's almost like tje battery is draining.... But it's not, like I said it shows over 12v

I'm stumped. Could my optima be bad even if it shows 12v? I haven't tried a different battery yet... Gonna do that next. Any thoughts or ideas?

Voltage alone will not tell you much. A dead cell will cause what you describe. I used to turn on the lights and crank while testing volts to see if the drop was excessive, but that's old-school. Try swapping in another fully-charged battery before you buy another.

Try measuring the voltage while the engine cranks. I think the magic number is 10 Volts: If voltage goes below that, your battery is suspect.

Have you done any of the Tips in the following link?

Is your starter soaked in oil even though it's only 2 years old?

http://www.naxja.org/forum/showthread.php?t=1115935

12v is not actually fully charged. A fully charged battery will read 12.6v. That being said i might swap a battery with a known good one if you have one laying around.
If that doesn't help i would start with a voltage drop test of the starting circuit. I had some internally corroded wires in my starting circuit that was causing excessive drop and cranking really slow.

I just went through something similar, it was a weak dead cell in my battery. Voltage was acceptable, maybe a tad low, but that bad cell cell lowered the available amperage and recharging the battery took a lot longer. A few quick short trips stop to shop and go onto the next stop and my battery would discharge to the point the starter barely turned the motor over. A load test on a fully charged battery is the only way to know for sure.

Like Cruiser said oil soaked or worn brushes can also cause this issue. It may crank with three brushes making contact, but it cranks very slowly and sucks a lot of amps. The wire leads to the brushes can get hooked up on the brush guide, if whomever assembled the motor wasn't careful and can keep a brush from seating properly..

I had the same problem with my 89, I followed the advice of cruiser54 and now no problems. I also replaced the positive and negative cables from the battery.

910cherokee said:

I had the same problem with my 89, I followed the advice of cruiser54 and now no problems. I also replaced the positive and negative cables from the battery.

Click to expand...

Just doing Tip 1 with the added cables makes quite a difference.

But, I don't suggest stopping there.........